Method for thermoelectric energy generation

ABSTRACT

Embodiments of the invention provide methods and apparatus for using a controllable heat source to generate electricity. One embodiment provides an energy generation module comprising a controllable heat source, one or more jackets of thermoelectric devices, and heat conducting fluids surrounding or otherwise thermally coupled to the jackets. The energy generation module can be used to convert heat from a heat source such as a gas combustion chamber into electricity. Embodiments of the invention are particularly useful for generating electricity when electrical power is not existent, cost prohibitive or otherwise in short supply. The generated electricity can be used by the user, stored in an electrical storage battery or sold to a local or remote power grid.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.13/586,828, entitled “SYSTEM FOR THERMOELECTRIC ENERGY GENERATION USINGNATURAL GAS”, filed Aug. 15, 2012, which claims the benefit of priorityto Provisional U.S. Patent Application No. 61/523,828, entitled “SYSTEMAND METHOD FOR THERMOELECTRIC ENERGY GENERATION”, filed Aug. 15, 2011;the aforementioned priority applications being hereby incorporated byreference for all purposes.

TECHNICAL FIELD

Embodiments described herein relate to thermoelectric energy generation.More particularly, embodiments described herein related to a system andapparatus for generating electricity from a heat source. Still moreparticularly, embodiments described herein related to a system andapparatus for controlling electricity generation from a heat source.

BACKGROUND

Thermal energy is one of the most common forms of energy existing in thenature and may result from process such as combustion. Heat is a form ofthermal energy which results from the transfer of thermal energy from asystem having a higher temperature to a system having a lowertemperature. Thermoelectric generators (TEGs), or thermoelectricdevices, are devices that are capable of directly converting heat intoelectricity. TEG modules, which can be in the form of strip, can beattached to stoves, fireplaces, or a furnace to harvest thermal energyfor providing electricity as a supplement or an alternative source.Current TEG strips have somewhat helped to alleviate heat wasting byconverting the waste heat into electricity; however, currentapplications of TEG are rudimentary and not fully effective. Theirefficiency is subject to various environmental settings,

In North America it is common to use natural gas to generate hot waterand/or hot air for domestic uses. In fact, nearly 70 percent of singlefamily homes use natural gas for heating purposes. Besides beingabundant, natural gas has an advantage over petroleum or coal, asnatural gas burns cleanly without producing harmful chemicals likesulfur dioxide or nitrogen oxide into the air. Although natural gas andelectricity in a given local area are regularly provided by the sameenergy company, they are typically sold and delivered to households astwo separate products using two separate delivery infrastructures (e.g.,power lines vs. gas lines). The inability of end customers to easilyconvert one product into another results in waste. Therefore, it isbeneficial to enable a user to selectively generate electricity from acontrollable heat source.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 illustrates one embodiment of an energy generation system;

FIG. 2A illustrates a side view of one embodiment of an energygeneration module;

FIG. 2B illustrates a cross section view of the embodiment shown in FIG.2A;

FIG. 3A illustrates a side view of another embodiment of an energygeneration module;

FIG. 3B illustrates a cross section view of the embodiment shown in FIG.3A;

FIG. 4 illustrates a multiple module configuration for an energygeneration system, according to one embodiment;

FIG. 5 illustrates an energy generation system with wireless remotecontrol ability, according to embodiments described herein;

FIG. 6 illustrates a mobile application of an energy generation system,according to embodiments; and

FIG. 7 illustrates a remote application of an energy generation system,according to embodiments.

DETAILED DESCRIPTION

Various embodiments of the invention provide a method and apparatus forusing a controllable heat source to generate electricity. Manyembodiments provide an energy generation module comprising acontrollable heat source, one or more jackets of thermoelectric devices,and heat conducting fluids. The fluids are configured and positioned toconduct heat from and/or to the jackets and may be placed to surroundall or a portion of the jackets and/or or to lie in between the jackets.The jackets of thermoelectric devices can be configured to be watertightso as to contain the fluids, or one or more sleeve-type enclosures canbe used to contain the fluids. The sleeve-type enclosures can be madefrom materials with high heat conductivity and the jackets ofthermoelectric devices may be coupled to the sleeve-type enclosures. Theenergy generation module can convert heat, for example, from a gascombustion chamber (also described as a combustor), into electricity.According to other embodiments, an energy generation system having oneor more energy generation modules, a direct current to alternate current(DC-to-AC) converter, and a control module are provided to selectivelygenerate electricity based, at least in part, on load demand and asupply condition(s) of the local power grid. According to yet anotherembodiment, a method for generating electricity using an energygeneration system having a plurality of energy generation modules withcontrollable heat sources is disclosed to selectively generateelectricity based at least in part on load demand and supply conditionof the local power grid.

Embodiments of invention described herein can enable a user, such as anindividual home owner, to generate electricity with high efficiency froma controllable heat source, for example, a natural gas combustor. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the embodiments. I t will beapparent, however, that the embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare shown in block diagram form to avoid unnecessarily obscuring theexemplary embodiments described herein.

FIG. 1 illustrates one embodiment of an energy generation system 100.The energy generation system 100 includes a natural gas input 110, acold water input 120, an electricity output 130, a hot water output 140,and an exhaust output 150. The energy generation system 100 alsoincludes one or more thermoelectric energy generation modules (EGMs)160, a control module 170, a DC-to-AC converter 180, and a water cooler190. The one or more EGMs are coupled to the natural gas input 110 andthe cold water input 120. According to present embodiments, the energygeneration system 100 can control the one or more EGMs 160 to convertheat from a controllable heat source (for example, by burning thenatural gas supplied by the natural gas input 110), to electricity.

The EGM(s) 160 is coupled to the natural gas input 110 for fuel gas, andto the cold water input 120 for coolant. According to presentembodiments, the EGM 160 includes a controllable heat source, at least afirst jacket of thermoelectric devices (or thermoelectric generators,“TEGs”) and at least a first heat conducting fluid contacting all or aportion of the outer side of the first jacket to create a temperaturedifference or gradient (ΔT) over a portion of the jacket ofthermoelectric devices. Typically, the temperature gradient will bebetween the inside wall of the jacket (the hot side) and the outsidewall (the cool side). However, other configurations for the gradient(ΔT) are also contemplated (e.g., inside wall is the cool side, outsidewall is the cool side, etc.). Through the thermoelectric effect, the ΔTcreates a voltage difference in the TEGs, and thereby the EGM 160converts heat into electricity. The heat conducting fluid can be anykind of fluid capable of heat conducting well known in the art, forexample, oil or water Also, the heat conducting fluid (as well a heatconducting material described herein) can surround all or a portion ofthe outside wall of the jacket. The heat conductive fluid (and/or theheat conductive material) can be in direct contact with the jacket orotherwise thermally coupled to the jacket through indirect contact(e.g., via another thermally conductive material or structure) to allowfor heat transfer to the heat conducting fluid. The controllable heatsource can selectively generate heat in response to a control signal.Such control signal may be transmitted from the control module 170 ofthe energy control system 100. Structures of the embodiments of the EGM160 are described in fuller detail below.

In the course of conversion, cold water supplied by the cold water input120, is used as at least in part for the coolant for the EGMs. Hot wateris produced as a by-product of the conversion, and is directed either tothe hot water output 140 for further use or to the water cooler 190 tobe cooled and redirected to the EGM 160 for reuse as coolant. The watercooler 190 can be any kind of suitable cooler including, for example, acompressor driven cooler. Exhaust, as another by-product of theconversion, is directed to the exhaust output 150 to be released intothe atmosphere. Because the process of burning natural gas typicallydoes not produce any harmful chemicals, it is safe to release theexhaust into the atmosphere. In some embodiments, the exhaust can beused as a heat source for heating purposes, for example, for heating hotwater. In still other embodiments carbon dioxide (CO₂) from the exhaustcan be filtered out using lithium hydroxide or other (CO₂)-sorbentmaterial known in the art such as various zeolite materials.

The main product of the conversion is electricity, which typically is inthe form of direct current. The electricity is directed from the EGM 160to the DC-to-AC converter 180 to become alternate current, and is thendirected to the electricity output 130. In some other embodiments, thedirect current can be directed to the electricity output 130, and theDC-to-AC converter 180 can be omitted. Additionally other electricaldevices 180 can be employed to modify electricity output 130. Suchelectrical devices can include for example, a transformer to step up orstep down the voltage of output 130 for power transmission to a localpower grid (e.g., up to 10 to 20 miles (16.09 to 32.19 kilometers) away)or a remote power grid (e.g., hundreds of miles away).

FIG. 2A illustrates a side view of one embodiment 200 of an energygeneration module (EGM). The EGM 200 includes a controllable heat source210, a plurality of thermoelectric generators (TEGs) 220, and heatconducting layer 230. The controllable heat source 210 burns natural gasas fuel to create heat. The heat conducting layer 230 is placed inproximity to the controllable heat source 210 so as to as leastpartially surround the heat source 210, so that the heat from thecontrollable heat source 210 is efficiently transferred to the heatconducting layer 230. The heat conducting layer 230 can be filled with aheat conducting fluid, like oil or water (that is desirably sealedwithin layer 230), or can simply be a heat conducting material, (forexample, copper) or can include a combination of heat conductive fluidand heat conducting material. In particular embodiments, the heatconducting layer 230 can have a corrugated or other textured surface soas to increase the surface area of layer 230 and thus, the amount/rateof heat transfer. The plurality of TEGs 220 form a jacket to surroundall or a portion of the heat conducting layer 230, so that the innerside of the jacket of TEGs are heated. The heated inner side of thejacket of TEGs and the outer cooler side of the jacket of TEGs result ina temperature difference or gradient (ΔT), which can be used to drivethe TEGs to generate electricity. Also, the plurality of TEG's 220 canbe substantially symmetrically distributed around the perimeter of heatconducting layer 230 and/or heat source 210, for example, having aspacing within 10, 5, 2, or 1 degrees apart. Various asymmetricdistributions are also considered. Also in various embodiments, TEG's220 can be distributed in a pattern whereby they are separated bythermally insulating wells as is discussed in greater detail herein.

FIG. 2B illustrates a cross section view of the embodiment 200 shown inFIG. 2A. As illustrated in FIG. 2A, the heat conducting layer 230 andthe jacket of the plurality of TEGs 220 are placed in proximity to thecontrollable heat source 210 so as to at least partially surround theheat source 210 for better conversion efficiency.

FIG. 3A illustrates a side view of another embodiment 300 of an energygeneration module (EGM). In this and related embodiments EGM 300includes a controllable heat source 310, a first jacket ofthermoelectric devices (TEGs) 320, a first heat conducting fluid 330,and optionally, a heat source housing 305. In some embodiments, the EGM300 further includes a second jacket of TEGs 340, and a second heatconducting fluid 350 as is explained in more detail below. According topresent embodiments, the controllable heat source 310 selectivelygenerates heat in response to a control signal, which is generated by acontrol module such as control module 170 in FIG. 1.

The first jacket of TEGs 320 has an inner side and an outer side. Theinner side of the first jacket 320 is placed in proximity to thecontrollable heat source 310 so as to at least partially surround theheat source 310 to absorb heat, for example, by conduction or otherforms of heat transfer (e.g., convection, etc). The outer side of thefirst jacket 320 is surrounded by the first heat conducting fluid 330.The first heat conducting fluid 330 acts as coolant or heat dissipationagent, and thereby creates a temperature difference (ΔT) between theinner and the outer side of the first jacket of TEGs 320, which in turnbecomes the source of electricity generation. In one embodiment, thefirst heat conducting fluid 330 is oil. In other embodiments, the firstheat conducting fluid 330 is water. Also various solutes can be added towater (e.g., salt) to increase its heat capacity.

In some embodiments, the second jacket of TEGs 340 is selected andpositioned so as to more completely absorb the heat generated from thecontrollable heat source 310. In such embodiments, the second jacket ofTEGs 340 is placed as enclosure for the first conducting fluid 330, sothat the inner side of the second jacket 340 surrounds the first heatconducting fluid 330 and absorbs heat from fluid 330. The second heatconducting fluid 350 is also placed to surround the outer side of thesecond jacket 340 to cool down the outer side of the second jacket 340and to create ΔT, so that the second jacket of TEGs 340 furthergenerates electricity. The jackets of thermoelectric devices (e.g., TEGs340) can be configured to be watertight so as to contain the fluids, orone or more sleeve-type enclosures can be used to contain the fluids.The sleeve-type enclosures can be made from materials with high heatconductivity and the jackets of thermoelectric devices (e.g., TEGs 340)may be coupled to the sleeve-type enclosures.

In various embodiments employing a first and a second jacket of TEGs 320and 340, a series of heat conducting conduits (not shown) can bethermally coupled to one or both of jackets 320 and 340 (either directlyor indirectly) so as to concentrate or otherwise enhance heat transferbetween jackets 320 and 340. The heat conducting conduits can be usedalone or in combination with heat transfer fluid 330. In particularembodiments, the heat conducting conduits can comprise various heatconducting metals known in the art and/or high heat capacity liquids(e.g. oil, water or salt water). In various embodiments, one or both ofenergy generating jackets 320 and 340 can have a rectangular or acylindrical shape configured to enhance heat transfer from one or moreof i) heat source 310 to first heat conducting fluid 330 and firstjacket 320; ii) first heat conducting fluid 330 and second jacket 340;and iii) between second jacket 340 and second heat conducting fluid 350.Other shapes are also considered for enhancing heat transfer between oneor more of the above elements. Additionally, one or both of jackets 320and 340 can have a corrugated, ribbed or other textured surface (eitherinside, outside or both) for enhancing heat transfer, for example, tofirst heat transfer fluid 330, or to second heat transfer fluid 350.Such shapes can have corrugated, ribbed, or other textured surface so asto increase surface area and further improve heat transfer.

Optionally, the heat source housing 305 is placed between the firstjacket of TEGs 320 and the controllable heat source 310 to protect theinner side of the jacket 320 against carbon accumulation from incompleteand/or inefficient combustion, which may happen when the natural gasdoes not burn completely. The heat source in housing 305 is desirablymade of materials with high heat conducting properties, for example,copper, to ensure high heat transfer efficiency from the heat source 310to the first jacket 320.

FIG. 3B illustrates a cross section view of the embodiment 300 shown inFIG. 3A. As illustrated in FIG. 3A, the optional heat source housing305, the first jacket of TEGs 320, the first heat conducting fluid 330,the second jacket of TEGs 340, and the second heat conducting fluid 350,are all placed in proximity to the controllable heat source 310 so as toat least partially surround the heat source 310 for betterheat-to-electricity conversion efficiency. It is noted that proper sealsare omitted from FIGS. 3A and 3B for simplicity; however, a personhaving ordinary skill in the art will understand that any suitable sealsor enclosures with high heat conductivity can be used to properlycontain the heat conducting fluids. It is further noted that the numberof jackets of TEGs and layers of heat conducting fluids are arbitraryand need not be the same. In some embodiments, the number of jackets isnot equal to the number of layers of heat conducting fluids. Also shownin the embodiment of FIG. 3B is configuration where the TEGS in secondjacket 340 are separated by thermally insulated wells to preventconduction or other thermal cross talk between TEGs which may resultingin a decrease in temperature gradient ΔT.

FIG. 4 illustrates a multiple module configuration for an energygeneration system (EGS) 400, according to one embodiment. The EGS 400includes a natural gas input 410, a cold water input 420, an electricityoutput 430, a hot water output 440, and one or more exhaust outputs 450.The energy generation system 400 also includes a plurality ofthermoelectric energy generation modules (EGMs) 460(1)-460(n), a controlmodule 470, a DC-to-AC converter 480, and a water cooler 490, andoptionally, a battery 405. The plurality of EGMs 460 are coupled to thenatural gas input 410 and the cold water input 420. According to presentembodiments, the energy generation system 400 can control the pluralityof EGMs 460 to convert heat from a controllable heat source, forexample, by burning the natural gas supplied by the natural gas input410, to electricity in a manner similar to the EGS 100 of FIG. 1described above. The operations of the EGMs 460 are similar to the EGM160 of FIG. 1, and are not redundantly described herein. However, theoperations of the control module 470 are now explained in more details.

Referring to both FIGS. 1 and 4, the control module 470 has aload/supply sensing input 475 to monitor load/supply condition, and iscoupled to the controllable heat sources of the plurality of EGMs 460 totransmit control signals. The control module 470 is configured to (i)monitor at least a load demand of the system and a supply condition of alocal power grid; (ii) determine when to generate electricity and atwhat capacity based on the results of the monitoring; and (iii) adjustone or more heat sources of the plurality of energy generation modulesbased on the determination. According to some embodiments, the controlmodule 470 can further monitor the buying prices for natural gas andelectricity in making the determination on whether it is economicallyprofitable to generate electricity, and if so, how much electricity isto be generated.

Therefore, when the power supply from the local power grid is not enough(e.g., during summer or during a power outage), the control module 470is operable to generate electricity. That is to say, the EGS 400 cangenerate electricity when the load demand of the system is greater thanthe supply condition of the local power grid, meaning the EGS 400 isoperating as a supplemental power source. Furthermore, there are certaintimes when it makes economic sense for the user to generate his or herown electricity from gas rather than buying electricity from the localpower company. Therefore, in some embodiments, the control module 470 isoperable to generate electricity when the cost of generating electricityusing the EGS 400 is lower than the cost of buying electricity directlyfrom a local power company.

Still further, in some places in North America, there are policies ofrepaying the users if they are to put electricity back onto the localpower grid. Therefore, in some embodiments, the control module 470further monitors a selling price for transmitting electricity back tothe local power grid, and the control module 470 is operable to generateelectricity when the cost of generation electricity is lower than theselling price for transmitting electricity back to the grid.

Optionally, the battery 405 can be placed in the EGS 400. The battery405 can be used for backup and/or power supplement purposes. In specificembodiments, because there is a transition delay in the process fromburning natural gas to generate heat, and then in converting the heatinto electricity, the battery 405 can be configured to support theelectrical power demands put on EGS 400 by users during this transitiontime. The battery 405 is charged when the electricity generated from theEGMs 460 is higher than the load demand, and is to release the energywhen the load demand is higher than the electricity generated from theEGMs 460. For embodiments the EGS 400 having a battery 405, the controlmodule 470 can be further configured to store electricity in the battery(e.g., by directing a charging current to the battery under a chargingregime tailored to the specific battery chemistry, e.g., lead acid,lithium ion, etc) during a first transition time in which an output fromthe plurality of energy generation modules is higher than what isdesignated by the control module, and then to release electricity fromthe battery during a second transition time in which the output from theplurality of energy generation modules is lower than what is designatedby the control module.

Therefore, the EGS 400 with control module 470 can dynamically generateelectricity based, at least in part, on load/supply demand 475. Thecontrol module 470 senses load conditions and accurately controls energygeneration. The control module 470 can control natural gas combustion(e.g., turn it off and on and control the rate) and/or adjust the flowrates of liquid in achieving its electricity generation targets.Advantageously, the EGS 400 can enable a user to efficiently convertnatural gas into electricity.

FIG. 5 illustrates an energy generation system 500 with wireless remotecontrol ability, according to embodiments described herein. The EGS 500is essentially the same as the EGS 400 of FIG. 4, except that the EGS500 is equipped with a wireless communication circuit 510 coupled to itscontrol module (not shown). With the wireless communication circuit 510,the control module can receive remote control commands to makeadjustment to energy generation operations. The remote control commandscan come from a centralized mission control, or other suitable sourcesincluding, for example, a user's personal digital assistance (PDA),personal computer, laptop, or a smart phone. In those cases in which theremote control commands come from one or more servers, the servers mayaccessible via the Internet (or the cloud). In other embodiments, theEGS 500 can communicate with one or more servers through wiredconnections such as a local area network (LAN).

FIG. 6 illustrates a mobile application of an energy generation system600, according to embodiments. The EGS 600 is mounted on to a mobileplatform, for example, a truck. The EGS 600 is suitable for a temporaryfield application. For example, in a natural gas farm environment wherethere is an ample supply of natural gas but lack of electricity, the EGS600 can convert natural gas into electricity for use.

FIG. 7 illustrates a remote application of an energy generation system700, according to one or more embodiments. Similar to the application ofthe EGS 600 of FIG. 6, one or more EGS(s) 700 can be installed at aremote site where ample supply of natural gas can be found, for example,a natural gas farm, sewage plant, farm, or an oil drilling platform. Inuse, the EGS 700 can convert natural gas found in such areas intoelectricity for use by consumers.

While the invention has been described with reference to specificembodiments thereof, it will be evident that various modifications andchanges may be made thereto without departing from the broader spiritand scope of the invention. For example, features or aspects of any ofthe embodiments may be applied, at least where practicable, incombination with any other of the embodiments or in place of counterpartfeatures or aspects thereof. Accordingly, the specification and drawingsare to be regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A method for providing electrical energy by anenergy generation system in communication with a local power grid, themethod comprising: monitoring at least a load demand of the energygeneration system and a supply condition of the local power grid,wherein the energy generation system includes a plurality of energygeneration modules, each of the plurality of energy generation modulesincluding a controllable heat source; determining whether to adjust oneor more controllable heat sources in order to modify an electricityoutput of the energy generation system based on the monitoring; andadjusting one or more controllable heat sources of the plurality ofenergy generation modules based on the determination.
 2. The method ofclaim 1, wherein the determining is performed when: the load demand ofthe energy generation system is greater than the supply condition of thelocal power grid.
 3. The method of claim 1, further comprising:monitoring a buying price for natural gas and a buying price forelectricity; and wherein the determining is performed when: a cost ofproviding electrical energy is lower than the buying price forelectricity.
 4. The method of claim 1, further comprising: monitoring aselling price for transmitting electricity back to the local power grid;and wherein the determining is performed when: a cost of providingelectrical energy is lower than the selling price for transmittingelectricity back to the local power grid.
 5. The method of claim 1,further comprising: storing the electricity output in a battery during afirst transition time in which an output from one or more of theplurality of energy generation modules is higher than what is designatedby a control module.
 6. The method of claim 5, further comprising:releasing the electricity output from the battery during a secondtransition time in which the output from one or more of the plurality ofenergy generation modules is lower than what is designated by thecontrol module.
 7. The method of claim 1, wherein adjusting the one ormore controllable heat sources of the plurality of energy generationmodules includes transmitting a control signal to at least one of theone or more controllable heat sources.
 8. The method of claim 1, furthercomprising: causing cold water to be admitted into the energy generationsystem, via a cold water input, so that the cold water flows within theenergy generation system to cool a jacket of thermoelectric devicesprovided with each energy generation module of the plurality of energygeneration modules.
 9. The method of claim 1, further comprising:converting the electricity output from direct current (DC) to alternatecurrent via a DC-to-AC converter.
 10. The method of claim 1, whereineach controllable heat source is a natural gas combustor.